The present invention relates to an electric circuit module in which an electric device is mounted on a heat sink.
An electric device, for example, a power semiconductor, is fixed to a copper plate by solder and the electric device together with lead wires for connection to an external circuit is encapsulated by a resin packing material, which is typified by epoxy resins, in a transfer molding method. Power semiconductors generate heat when applying electric current. The generated heat is dissipated to the outside through the copper plate or the packing material. Such a conventional power semiconductor constructed in this manner is mounted on a heat sink as shown in FIG. 32. More specifically, a screw is inserted through a through-hole provided on the packing material, and the screw is threadedly attached to the heat sink whereby the power semiconductor is fixed to the heat sink. Thereby, the power semiconductor is pressed against the heat sink and heat generated therefrom is efficiently transmitted to the heat sink.
Also, JP-Y2-7-3674, JP-A-2002-198477, JP-U-62-47140, JP-Y2-6-22995, JP-A-2001-332670, and JP-A-9-134985 disclose methods of mounting an electric device, which are known as conventional methods.
With an electric device, disclosed in JP-Y2-7-3674, among these, insulating holding means is provided inside a plurality of openings, which accommodate therein a plurality of electronic parts whereby the plurality of electronic parts are pressed against and fixed to a heat sink. Also, with the electric device disclosed in JP-Y2-7-3674, through-holes for permitting lead wires of the electronic parts to extend therethrough are provided in an electronic-part accommodating body whereby locating of the plurality of electronic parts are performed.
With a semiconductor device disclosed in JP-A-2002-198477, there is provided a plate-shaped elastic body, which is fixed to a heat sink by a screw and bent to cover power semiconductors, and a compressive force of which a power semiconductor is pressed against and fixed to the heat sink. Also, with the semiconductor device disclosed in JP-A-2002-198477, a positioning member is provided on a portion of the elastic body whereby locating of the lead wires of the power semiconductor is performed.
With a mount construction of a transistor disclosed in JP-U-62-47140, a power semiconductor is pressed against and fixed to a heat sink by a mount cover, which is made of an insulating material and provided with a power-semiconductor locating projection, a positional shift restricting portion, and an engaging portion for the heat sink.
With a fixing construction of a semiconductor element disclosed in JP-Y2-6-22995, a holding metal fitting is provided with a first projection, which is inserted into a hole provided in a packing material of a power semiconductor and by which the power semiconductor is pressed against and fixed to a heat sink.
Also, with the transistor mounting construction disclosed in JP-U-62-47140, a second projection is provided to press a packing material against the heat sink.
With a packaging construction of a semiconductor device disclosed in JP-A-2001-332670, a power semiconductor is pressed against and fixed to a heat sink by a plate-shaped spring member fixed to the heat sink. A heat insulating material having an insulating property is provided on an opposite surface of the plate-shaped spring member to a surface thereof in contact with the power semiconductor whereby the power semiconductor is hidden.
With a packaged construction of a semiconductor device disclosed in JP-A-9-134985, a plate-shaped spring is provided in a recess, which accommodates therein a power semiconductor, whereby the power semiconductor is fixed to a heat sink. Also, a projection fitted into the power semiconductor is provided in the recess whereby supporting of and prevention of coming-off of the power semiconductor are achieved.
With the screwing configuration in the conventional packaging construction shown in FIG. 32, however, the resin packing material causes a difference between a pressing force in a position just below the screw and a pressing force in a position distant from the position just below the screw, and deformation of the packing material. Therefore, with the screwing configuration in the conventional packaging construction shown in FIG. 32, it is not possible to obtain an efficient and stable heat dissipating quality (heat resistance). Also, the assembling quality is degraded by a decrease in accuracy to locate the lead wires.
With the construction disclosed in JP-Y2-7-3674, a spring provided in the opening of the electronic-part accommodating body generates an elastic force in an operating portion with a base of the spring in the electronic-part accommodating body as a fulcrum, so that creep fatigue is believed to be resulted in the spring. Creep fatigue appears markedly at high temperatures. Therefore, with the construction disclosed in JP-Y2-7-3674, it is believed that the material of the spring deteriorates to cause a decrease in pressing force and a stable heat dissipating quality cannot be obtained. Also, with the construction disclosed in JP-Y2-7-3674, the lead wires are believed to be unnecessarily bent upon insertion. Therefore, with the construction disclosed in JP-Y2-7-3674, the assembling quality is believed to be degraded.
With the construction disclosed in JP-A-2002-198477, the lead wires are believed to be unnecessarily bent upon insertion. Therefore, with the construction disclosed in JP-A-2002-198477, the assembling quality is believed to be degraded. Also, with the construction disclosed in JP-A-2002-198477, since a plurality of power semiconductors are assembled to the heat sink by the one elastic body, it is believed that the power semiconductors may come off and the positional accuracy may be lowered.
With the construction disclosed in JP-U-62-47140, it is believed that when a plurality of power semiconductors are to be fixed to the same heat sink, a pressing force cannot be applied evenly to the respective power semiconductors. Also, with the construction disclosed in JP-U-62-47140, it is not believed that it is possible to obtain an efficient and stable heat radiating quality (heat resistance).
With the construction disclosed in JP-Y2-6-22995, since only one positioning mechanism is prepared for the holding metal fittings and the power semiconductor, it is believed that turning is caused about the hole provided on the packing material of the power semiconductor. Therefore, with the construction disclosed in JP-Y2-6-22995, it is believed that that accuracy, with which the lead wires are positioned, is degraded and the assembling quality is degraded.
With the construction disclosed in JP-A-2001-332670, since the spring material is thin and an area, in which the spring material is connected to the heat sink, is small, it is believed difficult to radiate heat from the spring member and the insulating material. Therefore, with the construction disclosed in JP-A-2001-332670, temperature rise is believed to become conspicuous in the insulating material just above a portion of the spring member in contact with the power semiconductor.
With the construction disclosed in JP-A-9-134985, there is a need of individually preparing and fixing the plate-shaped springs, respectively, in the respective recesses, which accommodate therein the respective power semiconductors, so that the number of parts and assembly processes are increased and it is not believed that cost can be reduced.